/* Respond.js: min/max-width media query polyfill. (c) Scott Jehl. MIT Lic. j.mp/respondjs */
(function( w ){

"use strict";

//exposed namespace
var respond = {};
w.respond = respond;

//define update even in native-mq-supporting browsers, to avoid errors
respond.update = function(){};

//define ajax obj
var requestQueue = [],
xmlHttp = (function() {
var xmlhttpmethod = false;
try {
xmlhttpmethod = new w.XMLHttpRequest();
}
catch( e ){
xmlhttpmethod = new w.ActiveXObject( "Microsoft.XMLHTTP" );
}
return function(){
return xmlhttpmethod;
};
})(),

//tweaked Ajax functions from Quirksmode
ajax = function( url, callback ) {
var req = xmlHttp();
if (!req){
return;
}
req.open( "GET", url, true );
req.onreadystatechange = function () {
if ( req.readyState !== 4 || req.status !== 200 && req.status !== 304 ){
return;
}
callback( req.responseText );
};
if ( req.readyState === 4 ){
return;
}
req.send( null );
},
isUnsupportedMediaQuery = function( query ) {
return query.replace( respond.regex.minmaxwh, '' ).match( respond.regex.other );
};

//expose for testing
respond.ajax = ajax;
respond.queue = requestQueue;
respond.unsupportedmq = isUnsupportedMediaQuery;
respond.regex = {
media: /@media[^\{]+\{([^\{\}]*\{[^\}\{]*\})+/gi,
keyframes: /@(?:\-(?:o|moz|webkit)\-)?keyframes[^\{]+\{(?:[^\{\}]*\{[^\}\{]*\})+[^\}]*\}/gi,
comments: /\/\*[^*]*\*+([^/][^*]*\*+)*\//gi,
urls: /(url\()['"]?([^\/\)'"][^:\)'"]+)['"]?(\))/g,
findStyles: /@media *([^\{]+)\{([\S\s]+?)$/,
only: /(only\s+)?([a-zA-Z]+)\s?/,
minw: /\(\s*min\-width\s*:\s*(\s*[0-9\.]+)(px|em)\s*\)/,
maxw: /\(\s*max\-width\s*:\s*(\s*[0-9\.]+)(px|em)\s*\)/,
minmaxwh: /\(\s*m(in|ax)\-(height|width)\s*:\s*(\s*[0-9\.]+)(px|em)\s*\)/gi,
other: /\([^\)]*\)/g
};

//expose media query support flag for external use
respond.mediaQueriesSupported = w.matchMedia && w.matchMedia( "only all" ) !== null && w.matchMedia( "only all" ).matches;

//if media queries are supported, exit here
if( respond.mediaQueriesSupported ){
return;
}

//define vars
var doc = w.document,
docElem = doc.documentElement,
mediastyles = [],
rules = [],
appendedEls = [],
parsedSheets = {},
resizeThrottle = 30,
head = doc.getElementsByTagName( "head" )[0] || docElem,
base = doc.getElementsByTagName( "base" )[0],
links = head.getElementsByTagName( "link" ),

lastCall,
resizeDefer,

//cached container for 1em value, populated the first time it's needed
eminpx,

// returns the value of 1em in pixels
getEmValue = function() {
var ret,
div = doc.createElement('div'),
body = doc.body,
originalHTMLFontSize = docElem.style.fontSize,
originalBodyFontSize = body && body.style.fontSize,
fakeUsed = false;

div.style.cssText = "position:absolute;font-size:1em;width:1em";

if( !body ){
body = fakeUsed = doc.createElement( "body" );
body.style.background = "none";
}

// 1em in a media query is the value of the default font size of the browser
// reset docElem and body to ensure the correct value is returned
docElem.style.fontSize = "100%";
body.style.fontSize = "100%";

body.appendChild( div );

if( fakeUsed ){
docElem.insertBefore( body, docElem.firstChild );
}

ret = div.offsetWidth;

if( fakeUsed ){
docElem.removeChild( body );
}
else {
body.removeChild( div );
}

// restore the original values
docElem.style.fontSize = originalHTMLFontSize;
if( originalBodyFontSize ) {
body.style.fontSize = originalBodyFontSize;
}


//also update eminpx before returning
ret = eminpx = parseFloat(ret);

return ret;
},

//enable/disable styles
applyMedia = function( fromResize ){
var name = "clientWidth",
docElemProp = docElem[ name ],
currWidth = doc.compatMode === "CSS1Compat" && docElemProp || doc.body[ name ] || docElemProp,
styleBlocks	= {},
lastLink = links[ links.length-1 ],
now = (new Date()).getTime();

//throttle resize calls
if( fromResize && lastCall && now - lastCall < resizeThrottle ){
w.clearTimeout( resizeDefer );
resizeDefer = w.setTimeout( applyMedia, resizeThrottle );
return;
}
else {
lastCall = now;
}

for( var i in mediastyles ){
if( mediastyles.hasOwnProperty( i ) ){
var thisstyle = mediastyles[ i ],
min = thisstyle.minw,
max = thisstyle.maxw,
minnull = min === null,
maxnull = max === null,
em = "em";

if( !!min ){
min = parseFloat( min ) * ( min.indexOf( em ) > -1 ? ( eminpx || getEmValue() ) : 1 );
}
if( !!max ){
max = parseFloat( max ) * ( max.indexOf( em ) > -1 ? ( eminpx || getEmValue() ) : 1 );
}

// if there's no media query at all (the () part), or min or max is not null, and if either is present, they're true
if( !thisstyle.hasquery || ( !minnull || !maxnull ) && ( minnull || currWidth >= min ) && ( maxnull || currWidth <= max ) ){
if( !styleBlocks[ thisstyle.media ] ){
styleBlocks[ thisstyle.media ] = [];
}
styleBlocks[ thisstyle.media ].push( rules[ thisstyle.rules ] );
}
}
}

//remove any existing respond style element(s)
for( var j in appendedEls ){
if( appendedEls.hasOwnProperty( j ) ){
if( appendedEls[ j ] && appendedEls[ j ].parentNode === head ){
head.removeChild( appendedEls[ j ] );
}
}
}
appendedEls.length = 0;

//inject active styles, grouped by media type
for( var k in styleBlocks ){
if( styleBlocks.hasOwnProperty( k ) ){
var ss = doc.createElement( "style" ),
css = styleBlocks[ k ].join( "\n" );

ss.type = "text/css";
ss.media = k;

//originally, ss was appended to a documentFragment and sheets were appended in bulk.
//this caused crashes in IE in a number of circumstances, such as when the HTML element had a bg image set, so appending beforehand seems best. Thanks to @dvelyk for the initial research on this one!
head.insertBefore( ss, lastLink.nextSibling );

if ( ss.styleSheet ){
ss.styleSheet.cssText = css;
}
else {
ss.appendChild( doc.createTextNode( css ) );
}

//push to appendedEls to track for later removal
appendedEls.push( ss );
}
}
},
//find media blocks in css text, convert to style blocks
translate = function( styles, href, media ){
var qs = styles.replace( respond.regex.comments, '' )
.replace( respond.regex.keyframes, '' )
.match( respond.regex.media ),
ql = qs && qs.length || 0;

//try to get CSS path
href = href.substring( 0, href.lastIndexOf( "/" ) );

var repUrls = function( css ){
return css.replace( respond.regex.urls, "$1" + href + "$2$3" );
},
useMedia = !ql && media;

//if path exists, tack on trailing slash
if( href.length ){ href += "/"; }

//if no internal queries exist, but media attr does, use that
//note: this currently lacks support for situations where a media attr is specified on a link AND
//its associated stylesheet has internal CSS media queries.
//In those cases, the media attribute will currently be ignored.
if( useMedia ){
ql = 1;
}

for( var i = 0; i < ql; i++ ){
var fullq, thisq, eachq, eql;

//media attr
if( useMedia ){
fullq = media;
rules.push( repUrls( styles ) );
}
//parse for styles
else{
fullq = qs[ i ].match( respond.regex.findStyles ) && RegExp.$1;
rules.push( RegExp.$2 && repUrls( RegExp.$2 ) );
}

eachq = fullq.split( "," );
eql = eachq.length;

for( var j = 0; j < eql; j++ ){
thisq = eachq[ j ];

if( isUnsupportedMediaQuery( thisq ) ) {
continue;
}

mediastyles.push( {
media : thisq.split( "(" )[ 0 ].match( respond.regex.only ) && RegExp.$2 || "all",
rules : rules.length - 1,
hasquery : thisq.indexOf("(") > -1,
minw : thisq.match( respond.regex.minw ) && parseFloat( RegExp.$1 ) + ( RegExp.$2 || "" ),
maxw : thisq.match( respond.regex.maxw ) && parseFloat( RegExp.$1 ) + ( RegExp.$2 || "" )
} );
}
}

applyMedia();
},

//recurse through request queue, get css text
makeRequests = function(){
if( requestQueue.length ){
var thisRequest = requestQueue.shift();

ajax( thisRequest.href, function( styles ){
translate( styles, thisRequest.href, thisRequest.media );
parsedSheets[ thisRequest.href ] = true;

// by wrapping recursive function call in setTimeout
// we prevent "Stack overflow" error in IE7
w.setTimeout(function(){ makeRequests(); },0);
} );
}
},

//loop stylesheets, send text content to translate
ripCSS = function(){

for( var i = 0; i < links.length; i++ ){
var sheet = links[ i ],
href = sheet.href,
media = sheet.media,
isCSS = sheet.rel && sheet.rel.toLowerCase() === "stylesheet";

//only links plz and prevent re-parsing
if( !!href && isCSS && !parsedSheets[ href ] ){
// selectivizr exposes css through the rawCssText expando
if (sheet.styleSheet && sheet.styleSheet.rawCssText) {
translate( sheet.styleSheet.rawCssText, href, media );
parsedSheets[ href ] = true;
} else {
if( (!/^([a-zA-Z:]*\/\/)/.test( href ) && !base) ||
href.replace( RegExp.$1, "" ).split( "/" )[0] === w.location.host ){
// IE7 doesn't handle urls that start with '//' for ajax request
// manually add in the protocol
if ( href.substring(0,2) === "//" ) { href = w.location.protocol + href; }
requestQueue.push( {
href: href,
media: media
} );
}
}
}
}
makeRequests();
};

//translate CSS
ripCSS();

//expose update for re-running respond later on
respond.update = ripCSS;

//expose getEmValue
respond.getEmValue = getEmValue;

//adjust on resize
function callMedia(){
applyMedia( true );
}

if( w.addEventListener ){
w.addEventListener( "resize", callMedia, false );
}
else if( w.attachEvent ){
w.attachEvent( "onresize", callMedia );
}
})(this);